In this study

the characteristics of a linear compressor with vapor injection (VI) were investigated. A model of a linear compressor with VI validated by the experiment was proposed to explore the effects of VI pressure

piston stroke

and driving frequency on the operating parameters. The results showed that the VI caused delayed opening and early closing of the suction valve. Under the rating condition

when the injection pressure was 200 kPa and 400 kPa

the mass flow rate of suction decreased by 61% and 100% (to zero)

and that of discharge increased by 50% and 60%

respectively. Under constant electrical parameters

the stroke

offset

clearance

and resonant frequency of the free-piston increased with increasing injection pressure. Both the equivalent gas spring stiffness and gas stiffness increased with increasing injection pressure at constant clearance volume. For an increasing piston stroke

the mass flow rate of suction increased

while that of injection increased and then remained constant. When the compressor operates close to the resonant frequency

both the suction and injection mass flow rates reached their respective maxima

weakening the effect of injection on the decline of suction flow rate at high operating frequencies.